1. Field of the Invention
This invention relates to novel imidazopyridazine derivatives, their production and use.
The imidazopyridazine derivatives of the invention possess antiallergic, anti-inflammatory and anti-PAF (platelet-activating factor) activities and are useful as antiasthmatics by controlling bronchospasm and bronchoconstriction.
2. Description of the Prior Art
It has been disclosed in Japanese Unexamined Patent Publication No. SHO 61(1986)-152684 that imidazo[1,2-b]pyridazine compounds show anti-thrombogenic activity as well as cardiovascular activity, especially cardiotonic activity. However, any imidazo[1,2-b]pyridazine derivative possessing antiallergic, anti-inflammatory and anti-PAF activities has not been reported.
On the other hand, it is desired to develop more effective antiasthmatics, although various kinds of antiasthmatics have been launched into markets.
As the result of extensive studies on chemical modification at the 6 position of imidazo[1,2-b] pyridazine, the inventors of this invention have found imidazo[1,2-b]pyridazine derivatives possessing antiallergic, anti-inflammatory and anti-PAF activities which are not reported so far in the existing imidazo[1,2-b]pyridazine compounds. Said derivatives have been also found to control bronchospasm and bronchoconstriction.
Thus, this invention has been completed.